Chair armrests are fixed on two sides of a chair and are employed to adjust a height of the chair armrests. A conventional height adjustment mechanism is in a step adjusting type or a stepless adjusting type, wherein when the conventional height adjustment mechanism is in a step adjusting type, it contains an inner tube with two racks and an outer tube with plural adjustment teeth for meshing with the two racks, thus adjusting the chair armrests toward a desired height. However, a pith of each adjustment teeth is too large, so an adjusting range is limited. Moreover, when the conventional height adjustment mechanism is in a stepless adjusting type, it contains an inner tube, an outer tube, and a forcing element, such that the forcing element forces the inner tube and the outer tube to adjust the chair armrests toward a desired height. Nevertheless, the inner tube and the outer tube cannot be fixed securely.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.